Azo dyes are organic compounds containing the coloring azo function (N = N-). Azo is usually attached to the aromatic ring and the dye can then be cleaved to an aromatic amine, arylamine. Some Azo dyes also break down into arylamines during storage due to light and high temperature. Some arylamines are carcinogenic, the best known is aniline.
Azo dyes are used for dyeing textile fibers, cotton, silk, wool, viscose and synthetic fibers. It is known to be easy to use, cheap and supply powerful colors.
There are approximately 2000 azo dyestuffs on the market. Azo dyes are water soluble and therefore easy to absorb by the body. when exposured, inhalationed, ingestioned and contacted with skin and accumulates in the body. Arylamines are allergenic, irritating to the eyes, and can be toxic when inhaled and swallowed.
Azo dyes can cause long adverse effects harmful to aquatic organisms.
In REACH, Azo dyestuffs are limited to 30 ppm in the textile and leather parts of shoes.